CN114185018A - Phase noise digital real-time estimation method and system of frequency modulation continuous wave radar - Google Patents

Phase noise digital real-time estimation method and system of frequency modulation continuous wave radar Download PDF

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CN114185018A
CN114185018A CN202111400802.8A CN202111400802A CN114185018A CN 114185018 A CN114185018 A CN 114185018A CN 202111400802 A CN202111400802 A CN 202111400802A CN 114185018 A CN114185018 A CN 114185018A
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邱万智
罗海峰
张凡
熊翔
周源
蒋琦
黎晟昊
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Hangzhou Anda Technology Co ltd
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    • G—PHYSICS
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Abstract

The invention provides a method for estimating a phase noise power spectrum in real time by receiving a digital signal from an intermediate frequency, which comprises the steps of processing a target echo signal to obtain a digital difference frequency signal, processing a digital difference frequency signal matrix by utilizing two-dimensional fast Fourier transform to obtain a comprehensive frequency spectrum energy matrix, further obtaining target parameters, obtaining echo signals of targets after mutual mixing and superposition removal according to preset matrix operation, then calculating a phase noise sampling sequence and carrying out frequency spectrum analysis to obtain a phase noise power spectrum. The method does not need to add extra hardware, can directly extract the phase noise sampling value no matter under the condition of single or multiple targets, further estimates the power spectrum of the phase noise, has estimation precision which is not easily influenced by multiple targets and other types of noise, and can overcome some technical problems existing in the phase noise estimation method in the prior art.

Description

Phase noise digital real-time estimation method and system of frequency modulation continuous wave radar
Technical Field
The invention relates to Frequency Modulated Continuous Wave (FMCW) radar, and in particular to extracting phase noise sample values from an intermediate frequency received digital signal to estimate a phase noise power spectrum.
Background
Because of the unstable phase and frequency of the oscillator, the phase of the transmitting signal of the frequency modulation continuous wave radar has random jitter, the random phase jitter called phase noise has negative influence on the detection performance of the radar, and the estimation of the phase noise is an important subject for designing a radar with low phase noise and eliminating the influence of the phase noise. The existing FMCW radar phase noise estimation method can be mainly classified into two types: firstly, the echo signal is directly subjected to spectrum analysis, and real-time or off-line processing can be performed through the spectrum analysis, and the method has the defects that the estimation precision is influenced by multiple targets and other types of noise; secondly, a radio frequency delay line is added in a radar transceiver module to generate a virtual target echo, and the virtual target echo is compared with a real target echo to estimate phase noise.
The invention provides a method for estimating a phase noise power spectrum in real time from an intermediate frequency received digital signal, which does not need to add extra hardware, can directly extract a phase noise sampling value no matter under the condition of single or multiple targets, further estimates the power spectrum of the phase noise, has estimation precision which is not easily influenced by multiple targets and other types of noise, and can overcome some technical problems of two noise estimation methods mentioned in the background technology.
Disclosure of Invention
In view of the above drawbacks and deficiencies of the prior art, the present invention provides a method for estimating a phase noise power spectrum in real time from an intermediate frequency received digital signal, which can directly extract a phase noise sampling value to estimate the power spectrum of the phase noise without adding additional hardware, regardless of single or multiple target conditions, and the estimation accuracy is not easily affected by multiple targets and other types of noise.
In order to achieve the above object, the present invention provides a phase noise digital real-time estimation method for a frequency modulated continuous wave radar, which specifically comprises the following steps:
s1: transmitting a frame of sweep frequency signals by a transmitting antenna, wherein the frame of sweep frequency signals of the transmitting antenna array comprises a plurality of sweep frequency signals;
s2, receiving the receiving signal of the sweep frequency signal by a plurality of receiving antennas of a receiving antenna array, wherein the receiving signal is the superposition of a plurality of target echo signals;
s3, processing the target echo signal by a data processing unit to obtain a simulated difference frequency signal, wherein the simulated difference frequency signal is a simulated difference frequency signal of an I channel and a Q channel;
s4: performing low-pass filtering and analog-to-digital conversion processing on the analog difference frequency signal to obtain a digital difference frequency signal, wherein the digital difference frequency signal is a digital difference frequency signal of an I channel and a digital difference frequency signal of a Q channel;
s5: matrix arrangement is carried out on digital difference frequency signals corresponding to a plurality of sweep frequency signals in a frame, two-dimensional fast Fourier transform is carried out on the matrix arrangement to obtain a frequency spectrum matrix, and the frequency spectrum matrix is further calculated to obtain a comprehensive frequency spectrum energy matrix P;
s6, calculating the comprehensive spectrum energy matrix P to obtain target parameters;
s7: randomly determining a sweep frequency signal, acquiring a digital difference frequency signal of each receiving antenna in a receiving antenna array corresponding to the sweep frequency signal, and obtaining a target echo signal of each target after mutual mixing and superposition removal according to preset matrix operation;
s8: selecting any target echo signal after the mutual aliasing removal, and calculating a phase sequence of the target echo signal;
s9: calculating a phase noise sampling sequence according to the phase sequence;
s10: and carrying out spectrum analysis on the phase noise sampling sequence to obtain a phase noise power spectrum.
Wherein, a signal of one sweep time is called a sweep signal. The target echo signal received by the receiving antenna is subjected to frequency mixing and low-pass filtering to obtain an analog difference frequency signal, and the analog difference frequency signal is sent to a digital signal processing module to extract target information after analog-to-digital conversion (ADC).
Further, each frame of the sweep signal includes L (L is an integer and greater than zero) sweep signals s (t). The sub-sweep signal s (t) at time t may be represented as a function of the following time variable t:
Figure BDA0003371438790000031
wherein A is a constant representing the amplitude of the voltage, fcAs the center frequency, k ═ B/TcIs the slope of the sweep, B is the sweep bandwidth, TcIn order to frequency sweep time,
Figure BDA0003371438790000032
in order to be the initial phase position,
Figure BDA0003371438790000033
is the phase noise at time t.
Further, the L swept frequency signals, wherein L has a value of 16,32, 64, or 128.
Further, the receiving antenna array has D receiving antennas, and a receiving signal of the frequency sweep signal s (t) corresponding to each receiving antenna D (D ═ 1, 2.. and D) is a superposition of a plurality of target echo signals.
Further, the target echo signal of the kth sub-receiving antenna at time t is represented by a function of the following time variable t:
Figure BDA0003371438790000034
wherein M is the number of targets,
Figure BDA0003371438790000035
for the echo signal strength of the mth target received by the mth antenna, fdmFor the Doppler frequency of the mth target, the echo delay of the mth target is
τm＝2Rm/c (3)
RmThe distance of the mth target, and c the speed of light.
Further, the processing of the target echo signal by the data processing unit to obtain an analog difference frequency signal further includes low-noise amplification, frequency mixing, and intermediate-frequency amplification of the echo signal to obtain analog difference frequency signals of an I channel and a Q channel.
Further, for the D-th receiving antenna D (D ═ 1, 2.., D), the analog difference frequency signals corresponding to the I channel and the Q channel of one sweep signal s (t) can be expressed as:
Figure BDA0003371438790000041
Figure BDA0003371438790000042
further, the low-pass filtering and analog-to-digital conversion processing are performed on the analog difference frequency signal to obtain digital difference frequency signals of an I channel and a Q channel, and further includes that, for a D-th receiving antenna (D ═ 1, 2.. D), digital difference frequency signals of the I channel and the Q channel corresponding to a frequency sweep signal s (t) can be represented as:
Figure BDA0003371438790000043
Figure BDA0003371438790000044
wherein, N is 1, N is the number of sampling points, TsIn order to be the sampling period of time,
Figure BDA0003371438790000045
round () is rounded to get an integer. Digital difference signal y expressed in complex form(d)(n) is:
Figure BDA0003371438790000051
where j is the imaginary part representing the sign.
Further comprising arranging the digital difference frequency signals (as represented by equation (9)) of the receiving antennas D (D ═ 1, 2.., D) corresponding to a swept frequency signal into an N-dimensional column vector:
y(d)＝(y(d)(1) y(d)(2) ... y(d)(N))T,(d＝1,2,...D) (10)
wherein the upper right corner T represents the vector transpose operation.
Further, arranging digital difference frequency signals corresponding to all L sweep frequency signals in one frame into a matrix with N rows and L columns of dimensionality, and carrying out two-dimensional fast Fourier transform on the matrix to obtain a frequency spectrum matrix with the same dimensionality; repeating the two-dimensional fast Fourier transform operation on each receiving antenna in the receiving antenna array respectively to obtain D frequency spectrum matrixes: f(d)(D ═ 1,2,. D); and (3) performing point-by-point modular squaring on each spectrum matrix to obtain D spectrum energy matrixes: e(d)(D ═ 1,2,. D); and further averaging the D spectrum energy matrixes to obtain a comprehensive spectrum energy matrix P.
Further, calculating the comprehensive spectrum energy matrix P to obtain target parameters, and further obtaining parameters of each target according to coordinate index values of M peaks of the comprehensive spectrum energy matrix P.
Further comprising, a row index value I according to the M (M1, 2.. said., M) th peakmAnd column index value JmRespectively obtaining the distances R of the target mmAnd Doppler frequency fdm。
Further, arbitrarily determining a sweep frequency signal, obtaining digital difference frequency signals of each receiving antenna corresponding to the sweep frequency signal according to a formula (10), and obtaining echo signals x of each target after removing mutual mixing and overlapping through preset matrix operationm。
Further, the preset matrix operation is expressed as follows:
(x1 x2 ... xM)＝(y(1) y(2) ... y(D))C-1 (11)
wherein, y(d)D is a digital difference frequency signal defined by equation (10); x is the number ofmColumn vector for N dimensions:
xm＝(xm(1) xm(2) ... xm(N))T,(m＝1,2,...M) (12)
Figure BDA0003371438790000061
F(d)(Im,Jm) (D ═ 1,2,. D; m1, 2.. M) is a spectrum matrix F(d)To (I)m,Jm) And (4) each element. I ismAnd JmRespectively, the obtained row index value and column index value of the target m.
Further, calculating the phase sequence of each target echo signal after removing the mutual aliasing includes calculating an M (M ═ 1, 2.., M) th target echo signal xmPhase ofThe bit sequence is:
am(n)＝arctan(Imag(xm(n)/Real(xm(n)),(n＝1,2,...,N) (14)
wherein, arctan () is an arc tangent function, Real () is an operator for taking a Real part, and Imag () is an operator for taking an imaginary part;
calculation according to equation (6) and equation (7) yields:
Figure BDA0003371438790000062
wherein the content of the first and second substances,
Figure BDA0003371438790000063
further, equation (15) is converted to:
Figure BDA0003371438790000064
wherein:
bm(n)＝am(n)-Ф(n) (18)
according to the formula (17), for any-target m, the phase noise sampling value phi (nT)s) Are all bm(N) (N ═ 1, 2.., N) by an order of
Figure BDA0003371438790000071
The output sequence of the digital filter of (1).
Further, a phase noise sample sequence phi (nT) is calculateds) (N-1, 2.. said., N), further comprising, optionally, identifying a target, i.e., optionally an M e (1, 2.. said., M), and applying said b to said targetm(n) the sequence is passed through a digital filter with a transfer function of:
Figure BDA0003371438790000072
wherein z is transmissionThe argument of the function represents the look ahead operation of a cell. The output sequence of the filter is the sampled value of phase noise phi (nT)s) (N-1, 2, …, N). Wherein, bm(n) is calculated from the formula (18), the formula (15) and the formula (16), and the parameter τ is calculatedmAs calculated by the formula (3),
Figure BDA0003371438790000073
calculated by equation (8).
Further, the spectral analysis is a fast fourier transform.
To achieve the above object, according to another aspect of the present invention, there is provided a phase noise digital real-time estimation system for frequency modulated continuous wave radar. The invention relates to a phase noise digital real-time estimation system of a frequency modulation continuous wave radar, which comprises: the transmitting antenna is used for transmitting the frequency sweeping signal; the receiving array antenna is used for receiving a target echo signal of the sweep frequency signal; the system is characterized in that the phase noise digital real-time estimation system of the frequency modulation continuous wave radar is used for realizing a method for digitally estimating the phase noise of the frequency modulation continuous wave radar in real time.
The invention has the beneficial effects that: the invention provides a method for estimating a phase noise power spectrum in real time by receiving a digital signal from an intermediate frequency, which comprises the steps of processing a target echo signal to obtain a digital difference frequency signal, processing the digital difference frequency signal matrix by utilizing two-dimensional fast Fourier transform to obtain a comprehensive frequency spectrum energy matrix, further obtaining target parameters, obtaining target echo signals of all targets after mutual mixing and overlapping are removed according to preset matrix operation, calculating a phase noise sampling sequence and carrying out frequency spectrum analysis to obtain a phase noise power spectrum. The method does not need to add extra hardware, can directly extract the phase noise sampling value no matter under the condition of single or multiple targets, further estimates the power spectrum of the phase noise, has estimation precision which is not easily influenced by multiple targets and other types of noise, and can overcome some technical problems of two noise estimation methods mentioned in the background technology.
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FIG. 1: the schematic diagram of the frequency modulation continuous wave radar system and the relationship diagram of time (t) and frequency (f) of a transmitting signal.
FIG. 2: the embodiment of the phase noise digital real-time estimation method of the frequency modulation continuous wave radar is I.
FIG. 3 shows a comparison of the estimated phase noise power spectrum and the actual value.
FIG. 4: and comparing the estimated phase noise power spectrum with an actual value.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
It should be noted that: like reference numbers and letters refer to like items in the following figures or embodiments, and thus once an item is defined in one figure or embodiment, it need not be further defined and explained in subsequent figures or embodiments.
The invention belongs to the technology of a digital signal processing module in figure 1. The transmitting signal is a periodic sweep continuous wave. B is sweep bandwidth, TcIs the sweep time. A signal of one sweep time is referred to as a sweep signal. A transmit side Voltage Controlled Oscillator (VCO) generates a frequency modulated sine wave signal. The receiving antenna receives echo signals, the echo signals are subjected to frequency mixing and low-pass filtering to obtain difference frequency signals, the difference frequency signals are sent to a digital signal processing module to extract target information after analog-to-digital conversion (ADC). According to an embodiment of the present invention, as shown in fig. 2, a method for digitally estimating phase noise of a frequency modulated continuous wave radar in real time is provided, which specifically includes the following steps:
step 1, transmitting a frame of frequency sweeping signals by a transmitting antenna, wherein the frame of frequency sweeping signals of the transmitting antenna comprises a plurality of frequency sweeping signals;
receiving a receiving signal of the frame of the frequency-sweeping signal by a plurality of receiving antennas of a receiving antenna array, wherein the receiving signal is a superposition of a plurality of target echo signals;
step 3, processing the target echo signal by a data processing unit to obtain an analog difference frequency signal, wherein the analog difference frequency signal is an analog difference frequency signal of an I channel and a Q channel;
performing low-pass filtering and analog-to-digital conversion on the analog difference frequency signal to obtain a digital difference frequency signal, wherein the digital difference frequency signal is a digital difference frequency signal of an I channel and a digital difference frequency signal of a Q channel;
step 5, performing matrix arrangement on digital difference frequency signals corresponding to a plurality of frequency sweeping signals in one frame, performing two-dimensional fast Fourier transform on the matrix arrangement to obtain a frequency spectrum matrix, and further calculating the frequency spectrum matrix to obtain a comprehensive frequency spectrum energy matrix P;
step 6, calculating the comprehensive frequency spectrum energy matrix P to obtain target parameters;
randomly determining a frequency sweeping signal, acquiring digital difference frequency signals of each receiving antenna in a receiving antenna array corresponding to the frequency sweeping signal, and obtaining target echo signals of each target after mutual mixing and superposition removal according to preset matrix operation;
step 8, selecting any target echo signal after the mutual aliasing removal, and calculating a phase sequence of the target echo signal;
calculating a phase noise sampling sequence according to the phase sequence;
and (10) carrying out spectrum analysis on the phase noise sampling sequence to obtain a phase noise power spectrum.
According to another embodiment of the present invention, a method for digitally estimating phase noise of a frequency modulated continuous wave radar in real time is provided, which specifically includes the following steps:
step 1, a frame of frequency sweep signal is transmitted. A frame of swept frequency signals contains L (L is typically 16,32, 64 or 128) swept frequency signals. A swept frequency signal can be described as a function of the following time variable t:
Figure BDA0003371438790000101
where A is a constant representing the amplitude of the voltage, fcAs the center frequency, k ═ B/TcIn order to be the slope of the frequency sweep,
Figure BDA0003371438790000102
in order to be the initial phase position,
Figure BDA0003371438790000103
is phase noise.
Receiving an echo signal of the transmitted signal [ step 2 ].
Assuming that there are D receiving antennas, the received signal of each receiving antenna D (D ═ 1, 2.. times, D) for the one swept frequency signal is a superposition of multiple target echo signals, and can be described by a function of the following time variable t:
Figure BDA0003371438790000104
where M is the target number of bits,
Figure BDA0003371438790000105
for the echo signal strength of the mth target received by the mth antenna, fdmFor the Doppler frequency of the mth target, the echo delay of the mth target is
τm＝2Rm/c (3)
RmThe distance of the mth target, and c the speed of light.
And (3) processing the echo signals to obtain analog difference frequency signals. And the echo signals are subjected to low-noise amplification, frequency mixing and intermediate-frequency amplification to obtain analog difference frequency signals of an I channel and a Q channel. For the receiving antenna D (D ═ 1, 2.., D), the analog difference frequency signal corresponding to one sweep frequency signal can be expressed as:
Figure BDA0003371438790000111
Figure BDA0003371438790000112
and (4) carrying out low-pass filtering and analog-to-digital conversion on the analog difference frequency signal to obtain digital difference frequency signals of an I channel and a Q channel. For the receiving antenna D (D ═ 1, 2.., D), the digital difference frequency signal corresponding to one sweep frequency signal can be expressed as:
Figure BDA0003371438790000113
Figure BDA0003371438790000114
where N is 1sIn order to be the sampling period of time,
Figure BDA0003371438790000115
round () is rounded to get an integer. The digital difference signal represented in complex form is:
Figure BDA0003371438790000116
where j is the imaginary part representing the sign.
And (5) performing two-dimensional fast Fourier transform on the digital difference frequency signal. Arranging digital difference frequency signals (as shown in formula (9)) of a receiving antenna D (D ═ 1, 2.. times.d.) corresponding to a frequency sweep signal into an N-dimensional column vector:
y(d)＝(y(d)(1) y(d)(2) ... y(d)(N))T,(d＝1,2,...D) (10)
here the upper right corner T represents the vector transpose operation. Arranging digital difference frequency signals corresponding to all L sweep frequency signals in a frame into a matrix with the dimensionality of N rows and L columns, and carrying out two-dimensional fast Fourier transform on the matrix to obtain a frequency spectrum matrix with the same dimensionality. After the receiving antennas respectively perform the operations, D spectrum matrixes are obtained: f(d)(D ═ 1, 2.., D). And (3) performing point-by-point modulo square on each spectrum matrix to obtain D spectrum energy matrixes: e(d)(D ═ 1, 2.., D). And averaging the D spectrum energy matrixes to obtain a comprehensive spectrum energy matrix P.
And (6) solving target parameters. The coordinate index values of the M peaks of the integrated spectral energy matrix P correspond to the parameters of each target. Specifically, the row index value I of the M (M ═ 1, 2.., M) th peakmAnd column index value JmRespectively corresponding to the distances R of the target mmAnd Doppler frequency fdm。
And (7) solving and removing echo signals of all targets after mutual mixing and overlapping. Arbitrarily determining a sweep frequency signal, taking the digital difference frequency signal (see formula (10)) of each receiving antenna corresponding to the sweep frequency signal, and obtaining echo signal x of each target after removing mutual mixing and overlapping by the following matrix operationm：
(x1 x2 ... xM)＝(y(1) y(2) ... y(D))C-1 (11)
Where x ismColumn vector for N dimensions:
xm＝(xm(1) xm(2) ... xm(N))T,(m＝1,2,...M) (12)
Figure BDA0003371438790000121
F(d)(Im,Jm) (D ═ 1,2,. D; m1, 2.. M) is a spectrum matrix F(d)To (I)m,Jm) And (4) each element. I ismAnd JmThe row index value and the column index value of the target m obtained in step 6 are respectively.
[ procedure ] step (b)And 8, calculating the phase sequence of each target echo signal after the mutual mixing and overlapping removal. M (M ═ 1, 2.., M) th target echo signal xmThe phase sequence of (a) is:
am(n)＝arctan(Imag(xm(n)/Real(xm(n)),(n＝1,2,...,N) (14)
here, arctan () is an arctan function, Real () is a Real operator, and Imag () is an imaginary operator.
As can be seen from equations (6) and (7):
Figure BDA0003371438790000131
here, the
Figure BDA0003371438790000132
Equation (15) can be converted to:
Figure BDA0003371438790000133
here:
bm(n)＝am(n)-Ф(n) (18)
equation (17) shows that for any target m, the phase noise sample value phi (nT)s) Are all bm(N) (N ═ 1, 2.., N) by an order of
Figure BDA0003371438790000134
The output sequence of the digital filter of (1).
Step 9, a phase noise sampling sequence is calculated. Arbitrarily determine a target, i.e. optionally an M e (1, 2.. multidot.M), and apply b tom(n) the sequence is passed through a digital filter with a transfer function of:
Figure BDA0003371438790000135
where z is the argument of the transfer function and represents the look ahead operation of a cell. The output sequence of the filter is the sampling value of phase noise phi (nT)s) (N-1, 2, …, N). Where b ism(n) is calculated from formula (18), formula (15) and formula (16). Its required parameter taumAs calculated from the formula (3),
Figure BDA0003371438790000136
calculated by equation (8), Doppler frequency fdmObtained from step 6.
(step 10) sampling the phase noise sequence phi (nT)s) A spectral analysis (such as by fast fourier transform) is performed to obtain a phase noise power spectrum.
According to another embodiment of the present invention, there is provided a phase noise digital real-time estimation system for an fm continuous wave radar, including: the transmitting antenna is used for transmitting the frequency sweeping signal; the receiving array antenna is used for receiving a target echo signal of the sweep frequency signal; the digital real-time phase noise estimation method is characterized in that the digital real-time phase noise estimation system of the frequency modulation continuous wave radar is used for realizing the digital real-time phase noise estimation method of the medium frequency modulation continuous wave radar.
As shown in fig. 3, in a test case of the present invention, radar parameters: the sweep bandwidth is 180 MHz, the sweep time is 17.5 microseconds, one frame of sweep signal comprises 16 sweep signals, and the antenna is 1 sending and 2 receiving. A stationary target with a reflective area of 10 square meters is located 25 meters directly in front of the radar. Fig. 3 is an actual phase noise power spectrum and an estimated phase noise power spectrum. In another test case of the present invention, shown in fig. 4, the radar parameters are as in case one. The two targets have reflective areas of 10 square meters and 20 square meters, distances of 25 meters and 37.5 meters, azimuth angles of-10 degrees and 30 degrees, pitch angles of 0 degree and 30 degrees, and velocities of 13.91 meters/second and 34.79 meters/second, respectively. Fig. 4 shows an actual phase noise power spectrum and an estimated phase noise power spectrum. Fig. 3 and 4 illustrate that the estimated phase noise power spectrum coincides with the actual value.
According to the technical scheme of the embodiment of the invention, no additional hardware is needed, and no matter single or multiple target conditions exist, the phase noise sampling value can be directly extracted, so that the power spectrum of the phase noise is estimated, and the estimation precision is not easily influenced by multiple targets and other types of noise.
The above-described embodiments should not be construed as limiting the scope of the invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions can occur, depending on design requirements and other factors. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (18)

1. A phase noise digital real-time estimation method of a frequency modulation continuous wave radar comprises the following steps:
s1: transmitting a frame of sweep frequency signals by a transmitting antenna, wherein the frame of sweep frequency signals of the transmitting antenna comprises a plurality of sweep frequency signals;
s2, receiving the receiving signal of the frame of the sweep frequency signal by a plurality of receiving antennas of a receiving antenna array, wherein the receiving signal is the superposition of a plurality of target echo signals;
s3, processing the target echo signal by a data processing unit to obtain a simulated difference frequency signal, wherein the simulated difference frequency signal is a simulated difference frequency signal of an I channel and a Q channel;
s4: performing low-pass filtering and analog-to-digital conversion processing on the analog difference frequency signal to obtain a digital difference frequency signal, wherein the digital difference frequency signal is a digital difference frequency signal of an I channel and a digital difference frequency signal of a Q channel;
s5: matrix arrangement is carried out on digital difference frequency signals corresponding to a plurality of sweep frequency signals in a frame, two-dimensional fast Fourier transform is carried out on the matrix arrangement to obtain a frequency spectrum matrix, and the frequency spectrum matrix is calculated to obtain a comprehensive frequency spectrum energy matrix P;
s6, calculating the comprehensive spectrum energy matrix P to obtain target parameters;
s7: selecting any sweep frequency signal in the frame of sweep frequency signals, acquiring digital difference frequency signals of each receiving antenna in the receiving antenna array corresponding to the sweep frequency signals, and obtaining target echo signals of each target after mutual mixing and superposition removal according to preset matrix operation;
s8: selecting any target echo signal after the mutual aliasing removal, and calculating a phase sequence of the target echo signal;
s9: calculating a phase noise sampling sequence according to the phase sequence;
s10: and carrying out spectrum analysis on the phase noise sampling sequence to obtain a phase noise power spectrum.
2. A method for digital real-time estimation of phase noise of frequency modulated continuous wave radar as claimed in claim 1, wherein the frame of swept frequency signals comprises L (L is an integer and greater than zero) swept frequency signals. The sweep signal s (t) at time t may be represented as a function of the following time variable t:
Figure FDA0003371438780000021
wherein A is a constant representing the amplitude of the voltage, fcAs the center frequency, k ═ B/TcIs the slope of the sweep, B is the sweep bandwidth, TcIn order to frequency sweep time,
Figure FDA0003371438780000022
in order to be the initial phase position,
Figure FDA0003371438780000023
is the phase noise at time t.
3. A method of digital real-time estimation of the phase noise of frequency modulated continuous wave radar as claimed in claim 2, characterized in that the L swept frequency signals, where L has a value of 16,32, 64 or 128.
4. The method of claim 1, wherein the receiving antenna array has D receiving sub-antennas, and wherein the received signal of the swept frequency signal s (t) corresponding to the D-th receiving antenna (D1, 2.. multidot., D) is a superposition of a plurality of target echo signals.
5. A method according to claim 4, characterized in that the target echo signal of the sub-receiving antenna at time t is represented as a function of the following time variable t:
Figure FDA0003371438780000024
wherein M is the number of targets,
Figure FDA0003371438780000025
for the echo signal strength of the mth target received by the mth antenna, fdmThe Doppler frequency of the mth target, the echo delay of the mth target is taum＝2Rm/c (3)
RmThe distance of the mth target, and c the speed of light.
6. The method of claim 1, wherein the target echo signal is processed by the data processing unit to obtain an analog difference signal, and further comprising low noise amplifying, mixing, and intermediate frequency amplifying the echo signal to obtain analog difference signals of I and Q channels.
7. A method of digital real-time estimation of phase noise of frequency modulated continuous wave radar as claimed in claim 6, characterized in that for the D-th receiving antenna D (D ═ 1, 2.., D), the analog difference frequency signals of I channel and Q channel corresponding to a frequency sweep signal s (t) can be expressed as:
Figure FDA0003371438780000031
Figure FDA0003371438780000032
8. a method for digital real-time estimation of phase noise in frequency-modulated continuous wave radar according to claim 1, wherein the analog difference frequency signal is low-pass filtered and analog-to-digital converted to obtain digital difference frequency signals of I-channel and Q-channel, and further comprising, for the D-th receiving antenna (D ═ 1, 2.., D), which corresponds to the digital difference frequency signals of I-channel and Q-channel of a frequency sweep signal s (t), as follows:
Figure FDA0003371438780000033
Figure FDA0003371438780000034
wherein, N is 1, N is the number of sampling points, TsIn order to be the sampling period of time,
Figure FDA0003371438780000035
round () is rounded to get an integer. Digital difference signal y expressed in complex form(d)(n) is:
Figure FDA0003371438780000036
where j is the imaginary part representing the sign.
9. A method for digital real-time estimation of phase noise of frequency modulated continuous wave radar according to claim 8, characterized by arranging the digital difference frequency signals of the receiving antenna D (D ═ 1, 2.., D), corresponding to a swept frequency signal, into an N-dimensional column vector:
y(d)＝(y(d)(1) y(d)(2) ... y(d)(N))T,(d＝1,2,...D) (10)
wherein the upper right corner T represents the vector transpose operation.
10. The method according to claim 9, wherein the digital real-time estimation method of phase noise of frequency modulated continuous wave radar comprises performing two-dimensional fast fourier transform on a matrix formed by arranging the digital difference signals to obtain a frequency spectrum matrix, and calculating the frequency spectrum matrix to obtain a comprehensive frequency spectrum energy matrix P, further comprising arranging the digital difference signals corresponding to all L sweep signals in a frame into a matrix with N rows and L columns in one dimension, and performing two-dimensional fast fourier transform on the matrix to obtain a frequency spectrum matrix with the same dimension; repeating the two-dimensional fast Fourier transform operation on each receiving antenna in the receiving antenna array respectively to obtain D frequency spectrum matrixes: f(d)(D ═ 1,2,. D); and (3) performing point-by-point modular squaring on each spectrum matrix to obtain D spectrum energy matrixes: e(d)(D ═ 1,2,. D); and further averaging the D spectrum energy matrixes to obtain a comprehensive spectrum energy matrix P.
11. The method according to claim 8, wherein the step of calculating the integrated spectral energy matrix P to obtain target parameters further comprises obtaining parameters of each target according to the coordinate index values of M peaks of the integrated spectral energy matrix P.
12. Method for digital real-time estimation of the phase noise of frequency modulated continuous wave radar according to claim 11, characterized in that the seating of the M peaks of the synthetic spectral energy matrix P is based onObtaining parameters of each target according to the index values, and further obtaining a row index value I according to the M (M1, 2mAnd column index value JmRespectively obtaining the distances R of the target mmAnd Doppler frequency fdm。
13. The method according to claim 8, wherein a frequency-swept signal is arbitrarily determined, a digital difference frequency signal corresponding to the frequency-swept signal is obtained from each receiving antenna, and the echo signal x of each target after removing the mutual overlap is obtained by a predetermined matrix operationm。
14. A method for digital real-time estimation of the phase noise of frequency modulated continuous wave radar according to claim 13, wherein the predetermined matrix operation is represented as follows:
(x1 x2 ... xM)＝(y(1) y(2) ... y(D))C-1 (11)
wherein, y(d)D is a digital difference frequency signal defined by equation (10); x is the number ofmFor an N-dimensional column vector:
xm＝(xm(1) xm(2) ... xm(N))T,(m＝1,2,...M) (12)
Figure FDA0003371438780000051
F(d)(Im,Jm) (D ═ 1,2,. D; m1, 2.. M) is a spectrum matrix F(d)To (I)m,Jm) And (4) each element. I ismAnd JmRespectively, the obtained row index value and column index value of the target m.
15. A method of digitally estimating phase noise of an FM CW radar as claimed in claim 8, wherein said removing is calculated after aliasingThe phase sequence of each target echo signal further comprises selecting any target echo signal xm(M ═ 1, 2.., M), the phase sequence of which was calculated as:
am(n)＝arctan(Imag(xm(n)/Real(xm(n)),(n＝1,2,...,N) (14)
wherein, arctan () is an arc tangent function, Real () is an operator for taking a Real part, and Imag () is an operator for taking an imaginary part;
calculation according to equation (6) and equation (7) yields:
Figure FDA0003371438780000061
wherein the content of the first and second substances,
Figure FDA0003371438780000062
further, equation (15) is converted to:
Figure FDA0003371438780000063
wherein:
bm(n)＝am(n)-Ф(n) (18)
according to the formula (17), for any target m, the phase noise sampling value phi (nT)s) Are all bm(N) (N ═ 1, 2.., N) by an order of
Figure FDA0003371438780000064
The output sequence of the digital filter of (1).
16. Method for digital real-time estimation of the phase noise of frequency modulated continuous wave radar according to claim 15, characterized in that the sequence of phase noise samples phi (nT) is calculateds) (N ═ 1, 2.., N), further comprising, arbitrarily identifying a target, i.e., anySelecting an M e (1, 2.. multidot.M), and combining the bm(n) the sequence is passed through a digital filter with a transfer function of:
Figure FDA0003371438780000065
wherein z is an argument of the transfer function, representing a look ahead operation of a cell. The output sequence of the filter is the sampling value of phase noise phi (nT)s) (N-1, 2, …, N). Wherein, bm(n) is calculated from the formula (18), the formula (15) and the formula (16), and the parameter τ is calculatedmAs calculated by the formula (3),
Figure FDA0003371438780000066
calculated by equation (8).
17. Method for digital real-time estimation of the phase noise of frequency modulated continuous wave radar according to claims 1-15, characterized in that the spectral analysis is a fast fourier transform.
18. A system for digital real-time estimation of phase noise of an fm continuous wave radar comprising a transmitting antenna, an array of receiving antennas, and a data processing module, the system for digital real-time estimation of phase noise of an fm continuous wave radar being adapted to implement the method according to any one of claims 1 to 17.
CN202111400802.8A 2021-08-17 2021-11-24 Phase noise digital real-time estimation method and system of frequency modulation continuous wave radar Pending CN114185018A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116819431A (en) * 2023-08-31 2023-09-29 杭州岸达科技有限公司 Phase interferometer direction finding method based on anomalous phase mode excitation
CN118011397A (en) * 2024-04-08 2024-05-10 中国科学院空天信息创新研究院 Echo abnormality detection and compensation method

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116819431A (en) * 2023-08-31 2023-09-29 杭州岸达科技有限公司 Phase interferometer direction finding method based on anomalous phase mode excitation
CN116819431B (en) * 2023-08-31 2023-12-08 杭州岸达科技有限公司 Phase interferometer direction finding method based on anomalous phase mode excitation
CN118011397A (en) * 2024-04-08 2024-05-10 中国科学院空天信息创新研究院 Echo abnormality detection and compensation method

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